Filtration devices are used in hydraulic systems, including pilot circuits, return lines and case drain lines of hydraulic systems and the like, to minimize contamination of the hydraulic fluid and the system. However, the efficiency of known conventional filtration devices is relatively low under some conditions. Such low efficiency is generally due to several factors, including dynamic conditions such as flow surges, cold fluid conditions, vibration, and impact forces transmitted through the fluid to the filtration devices from the working end of the hydraulic system. One known way of increasing filtration efficiency is to maintain steady flow through the filter. See for instance, Miller U.S. Pat. No. 5,395,519, issued Mar. 7, 1995 to Caterpillar Inc. Another known way of increasing filtration efficiency is to not force cold hydraulic fluid through the filter. However neither of these alternatives has proven to be completely satisfactory.
Accordingly, the present invention is directed to overcoming one or more of the problems as set forth above.